Why is the corona vaccine given in two doses?

Getting the Corona vaccine helps stop the Covid-19 epidemic and may be considered a social duty. Undoubtedly, the most effective way that experts suggest to prevent coronary heart disease is to get vaccinated. As you probably know, most vaccines produced in the world and approved by the World Health Organization are injected in 2 doses. Why is the corona vaccine injected twice?

How the Corona vaccine works

So far, vaccines injected in Iran include Sinofarm, Astrazanka, Sputnik, Bharat and Barakat. Some of these vaccines, such as Astrazanka and Sputnik, are made with mRNA technology, while others, such as Sinofarm, are derived from inactivated virus. Vaccines produced by MRNA technology, after injection, cause the body’s cells to make a protein that triggers an immune response in the human body. These vaccines do not contain live viruses and will not affect genetic material or human genes.

Inactivated viruses have been used in vaccines such as Sinofarm and Barakat. Injections of this type of vaccine also lead to an immune system in the body and provide protection against the coronavirus. Both vaccines made with mRNA technology and those that use inactivated virus both show their ultimate safety 2 weeks after the second dose.

Corona vaccine injection dose

Studies have shown that most vaccines, even vaccines such as Pfizer and Moderna, produce a relatively weak immune response when given in a single dose; However, if used in 2 doses, a stronger immune response will be created. Basically, the first dose of Corona vaccine starts the process of building protection, but the injection of the second dose will strengthen this protection.

A simple example can better explain why the corona vaccine is given in two doses. Imagine that you are going to push a heavy table with your friend and move it from one side of the room to another. Do your best to succeed in the middle. Then a few more friends will join you and with their help you can move the table to the place you want. Vaccines that require 2 doses have the same condition and are injected twice for greater safety and effectiveness. In addition to the corona vaccine, some other vaccines require two doses; For example: measles, mumps and rubella (MMR) vaccine, hepatitis vaccine and shingles vaccine.

Single-dose Corona vaccines

Some relatively small number of corona vaccines require only one injection. The Covid-19 vaccine, developed by Johnson & Johnson, is one of these vaccines. In Iran, news also indicates that a single dose of Sinofarm vaccine will be injected for ages 3 to 17 years.

The interval between the first dose of the corona vaccine and the second dose

We said that 2 doses of Corona vaccine should be given so that the vaccine can show its maximum effectiveness and create immunity. The interval between injections of these two doses depends on the type of vaccine the person has received. The interval between 2 doses of Corona vaccine in different types that are injected in Iran is as follows:

• Sinofarm vaccine: 28 days
• Astraznka vaccine: 12 weeks
• Blessing vaccine: 21 to 28 days
• Sputnik vaccine: 21 to 28 days
• Indian Bharat vaccine: 28 days

With the injection of the first dose, the body shows a weak immune response to the external agent and then after the injection of the second dose, the immune response is maximized. However, you should note that none of the corona vaccines, even vaccines such as Pfizer and Modern, can provide 100% immunity against Covid-19, and after injecting both doses, the protocols are still required.

What happens if the second dose of Corona vaccine is not given on time?

The general recommendation is to inject the second dose of Corona vaccine exactly at the time specified on the vaccine card. But for whatever reason you may not be able to get your vaccine on time; For example, you may get coronavirus between two doses; What to do in this case? The standard interval between two doses is usually the best time to inject, but after this time the second dose can be injected. Unless it is too late for the vaccine to lose its effectiveness. In this case, the first dose should be re-injected.

Experts on the Sinofarm vaccine have stated that the second dose of the vaccine will not cause any problems, even if it is delayed for up to 90 days.

A short interval between two doses of Corona vaccine will not make the first dose of this vaccine ineffective; So no need to worry.

Is it possible to use a different corona vaccine in the second dose?

It is strongly recommended that both doses of the Corona vaccine be given from the same vaccine. However, if for any reason the vaccines are not of the same type, for example, the vaccine is not available at the time of the second dose, then it is necessary to use a vaccine whose platform is the same as the previous vaccine. Therefore, the first dose of Corona vaccine should not be given to Astraznka and then the second dose of Barakat vaccine should not be used. Because the Barakat vaccine platform is weakened by the virus, while the Astrazanka vaccine is made with mRNA technology. But since Sinofarm and Barakat are both derived from the weakened or killed virus, one can be used in one dose and the other in the next dose.

Differences in side effects of Sinofarm and Astrazenka vaccines

As mentioned earlier, the technology for making Sinofarm and Astrazhenka vaccines is quite different. In general, the side effects of these two vaccines are almost identical and include the following:

• Swelling and pain at the injection site
• Fever
• nausea
• لرز
• Headache
• joint’s pain
• feeling exhausted

But the symptoms of Astraznka are more severe. In any case, the side effects of all Corona vaccines should be eliminated in less than 3 days, and if it lasts longer than this, you should see a doctor because the person may have a specific disease or have received Corona at the same time.

last word

The dose of corona vaccine should usually be given twice. Of course, this issue is related to the type of vaccine, but the vaccines available in Iran are currently not single dose. The second dose should never be delayed because the maximum immunity created by the vaccine is two weeks after the second dose.